Model 990Enh-Ticha Discrete Operational Amplifier
Professional Audio Products Datasheet
Model 990Enh-Ticha
Discrete Operational Amplifier
Features:
• Low Impedance Line Amplifiers and Drivers
• Active Filters and Equalizers
• Summing/Mixer Amplifiers
• High Performance Microphone Preamplifiers
• High Performance A/D and D/A front end Preamplifier
• High Performance D/A I-V convertors
• High Current Buffer Amplifier
Package Diagram:
CL
PCB TOP VIEW
0.563
(14.30mm)
0.100
(2.54mm)
0.00
CL
(0mm)
-0.100
-(2.54mm)
Dual matched pair temperature stable current mirrors, dual matched
pair active current loads give the Model 990Enh it’s outstanding
power supply rejection performance. The enhanced low distortion
Class-A output driver stage can sink or source 250mA allowing this
module to drive transformers easily.
0.200
(5.08mm)
CL 0.00
(0mm)
-0.200
-(5.08mm)
-0.400
-(10.16mm)
OUT
(+)IN
(-)VEE
GND
(-)IN
(+)VCC
-0.563
-(14.30mm)
-0.400
-(10.16mm)
-0.563
-(14.30mm)
0.400
(10.16mm)
0.563
(14.30mm)
In addition to the enhanced input stage, the 990Enh-Ticha uses high
precision temperature stable power supply independent current
sources. Supply independent current sources allow the bias to
remain locked at the optimum operating point regardless of power
supply voltage.
Applications:
CL 0.00
(0mm)
The 990Enh is a high performance discrete operational amplifier
designed for professional audio applications and areas where
ultralow noise and low distortion is required. It was designed as
an enhanced higher performance upgrade replacement for the
Jensen JE990, Automated Processes Inc. API-2520, John Hardy
Co. 990A-990C, FiveFish Studios DOA series, Seventh Circle Audio
SC10, SC25, SC99, and Avedis Audio 1122 op-amp gain block. The
pinouts conform to the 990 package, allowing direct replacement.
See TABLE 1. on page 4 for additional discrete opamps which can
be upgraded.
The all-discrete SMT design is similar to the JE990 basic topology
but has been completely redesigned to use an ultra-precision
differential super-matched transistor pair specifically designed to
meet the requirements of ultra-low noise and ultra-low THD audio
systems.
• Ultra Low Total Harmonic Distortion, 0.00045 THD+N @ 1kHz
• Ultra Low Noise 890pV/rtHz typical
• High Current Output Drive (250mA into 75 ohms)
• +26dBu Output Levels (into 600 ohms)
• Standard Gain Block Footprint
• Operates over ±10V to ±24V supply rails
• Lower output offset voltage than existing counterparts
• Lower input leakage current than existing counterparts
• Particular emphasis on audio performance
• Designed, assembled and produced in the USA
• 3 Year Warranty
CL
SIDE VIEW
0.600
(15.24mm)
0.00
(0mm)
0.00
(0mm)
-0.280/0.30
(-7.10/7.62mm)
0.040 Dia
→ ←(1.016mm
Dia)
CL
Connection Diagram:
+IN
+
-IN
-
OUTPUT
(-)VEE
GND
(+)VCC
©1998-2012 Sonic Imagery Labs
Specifications subject to change without notice
REV C, 8.15.2013
Page Sonic Imagery Labs
P.O. Box 20494
Castro Valley, California 94546
P:(510)728-1146 F:(510)727-1492
www.sonicimagerylabs.com
Model 990Enh-Ticha Discrete Operational Amplifier
Professional Audio Products Datasheet
Model 990Enh-Ticha
Discrete Operational Amplifier
Integrated power transistor heatsinks coupled to a anodized
aluminum enclosure keeps the 990Enh-Ticha operating within a
wide SOA (safe operating area) and does not suffer from Beta droop
when driving transformers or low impedance loads. Each amplifier
is fully tested and meets or exceeds published specifications.
Because of the 990Enh high current drive capability, supporting
circuitry impedances can be scaled down within the application
circuit. This can reduce the overall system noise, without increased
distortion and provides higher headroom compliance performance.
If the user is upgrading or replacing vintage or retro-clone gear,
take note of the pin length required for your particular application.
Older gear typically used modules with 0.480 to 0.510 inch long
0.040 pins. Sonic Imagery Labs offers this longer pin length variant
at no additional charge. See the Model 990Enh-Ticha and 995FETTicha Mechanical Options Application Note AN-18 for additional
mechanical details.
For a FET based discrete opamp version with this architecture,
see the Sonic Imagery Labs Model 995FET-Ticha datasheet. Sonic
Imagery Labs also can provide a variation of this model that can
operate down to ±4.5V for low power, low voltage applications.
Contact us and ask about the Model 990LV-Enh-Ticha.
0.905
(22.99mm)
SIDE VIEW
Pin Socket installed from
top side of PCB in 0.068”
Diameter hole 0.140 pad
VCC
0.1%
0.305
(7.75mm)
0.00
(0mm)
0.1%
ACTIVE
CURRENT LOAD
Height Above
PC Board with STD Pin length
and Pin Socket mounted on
top side of PCB
ACTIVE
CURRENT LOAD
PCB Reference Plane
0.770
(19.59mm)
SIDE VIEW
Pin Socket installed from
top side of PCB in 0.096”
Diameter hole 0.140” pad
(-)INPUT
+V
0.05%
LOW NOISE REFERENCE LOCKED
SUPPLY-INDEPENDENT
TEMPERATURE STABLE
CURRENT SOURCE
DIODE PAIR
+V
DIODE PAIR
ULTRA LOW
LEAKAGE PAIR
(+)INPUT
PRECISION
SUPER-MATCHED
PAIR
0.168
(4.267mm)
PCB Reference Plane
0.00
(0mm)
DUAL
PNP MATCHED
PAIR
DUAL
NPN MATCHED
PAIR
OUTPUT
Height Above
PC Board with STD Pin length
and Pin Socket mounted from
bottom side of PCB
DETAIL A. (Above) Standard pin length height specifications and
mounting options for Sonic Imagery Labs Model 990Enh-Ticha
opamp module.
0.05%
NOISE
SHAPING
LOW NOISE REFERENCE LOCKED
SUPPLY-INDEPENDENT
TEMPERATURE STABLE
CURRENT SOURCE
DUAL
NPN MATCHED
PAIR
DUAL
NPN MATCHED
PAIR
Recommended Operating Conditions:
DUAL
NPN MATCHED
PAIR
DUAL
NPN MATCHED
PAIR
0.1%
0.1%
0.1%
0.1%
VEE
Simplified Schematic of the Model 990Enh-Ticha
Positive Supply Voltage Negative Supply Voltage Signal Current (inverting mode)
VCC
VEE
Iin
+10V to +24V
-10V to -24V
50nA to >200 uA
Stresses above those listed under “Absolute Maximum Ratings” may
cause permanent damage to the device. These are stress ratings only;
the functional operation of the device at these or any other conditions
above those indicated in the operational sections is not implied. Exposure
to absolute maximum rating conditions for extended periods may affect
device reliability.
©1998-2015 Sonic Imagery Labs
Specifications subject to change without notice
REV D, 8.20.2015
Page Sonic Imagery Labs
P.O. Box 20494
Castro Valley, California 94546
P:(510)728-1146 F:(510)727-1492
www.sonicimagerylabs.com
Model 990Enh-Ticha Discrete Operational Amplifier
Professional Audio Products Datasheet
Model 990Enh-Ticha
Discrete Operational Amplifier
Absolute Maximum Ratings
Supply Voltage Differential Input Voltage
Input Voltage Range
Operating Temperature Range
Storage Temperature Range
VCC-VEE
56V
VID13.9Vrms (+25dBu) @ unity gain
VIC
±12.5V
TOPR
-40~85°C
TSTG
-60~150°C
DC Electrical Characteristics (Ta=25°C, Vs=±24V unless otherwise noted)
Symbol Parameter
Conditions
VOS
IOS
IB
AVOL
VOM
VOM
VCM
CMRR
PSRR
IQ
Input Offset Voltage
Input Offset Current
Input Bias Current
Voltage Gain (open loop)
Output Voltage Swing
Output Voltage Swing
Input Common-Mode Range
Common-Mode Rejection Ratio
Power Supply Rejection Ratio
Supply Current
RS=0Ω Av=Unity
-3dB @ 43Hz
Vs=±24V RL=600Ω Av=10
Vs=±24V RL=75Ω Av=10
RL=600Ω
Vo=0, inputs gnd, Vcc=24V
Vo=0, inputs gnd, Vee=24V
Min
Typ
Max
Units
0.8
118
41
38
±12
80
88
17
23
0.22
1
10
120
42
38.5
±12.5
100
104
18
25
0.45
8
50
122.5
19.5
26.5
mV
nA
uA
dB
Vpp
Vpp
V
dB
dB
mA
mA
Min
Typ
Max
Units
18
17
250
19
18
>50
260
20
19
V/uS
V/uS
MHz
mA
Min
Typ
Max
Units
-
0.00045
0.0003
0.00034
850
<1.0
>180
13.5
>10M
1000
-
%
%
%
pV√ Hz
pA√ Hz
kHz
MHz
Ω
AC Electrical Characteristics (Ta=25°C, Vs=±24V unless otherwise noted)
Symbol Parameter
SR
SR
GBW
Slew Rate
Slew Rate
Gain Bandwidth Product
Maximum Peak Output Drive Current
Conditions
RL=600Ω
RL=75Ω
10kHz to 100kHz
RL=75Ω
Design Electrical Characteristics (Ta=25°C, Vs=±24V unless otherwise noted)
Symbol Parameter
Conditions
THD
THD
THD
en
in
PBW
fU
Zin
RL =600Ω Unity Gain @1kHz
RL =600Ω 20dB Gain inverting @1kHz
RL =600Ω 20dB Gain non-invert @1kHz
Input shorted to ground
Large-signal BW RL =600Ω
Small-signal BW at unity gain (ft)
Noninverting Input
Distortion+Noise
Distortion+Noise
Distortion+Noise
Input Refered Noise Voltage
Input Refered Noise Current
Power Bandwidth
Unity Gain Frequency
Input Resistance
©1998-2015 Sonic Imagery Labs
Specifications subject to change without notice
REV D, 8.20.2015
Page Sonic Imagery Labs
P.O. Box 20494
Castro Valley, California 94546
P:(510)728-1146 F:(510)727-1492
www.sonicimagerylabs.com
Model 990Enh-Ticha Discrete Operational Amplifier
Professional Audio Products Datasheet
Model 990Enh-Ticha
Discrete Operational Amplifier
THD+N Large Signal Performance (Ta=25°C, Vs=±24V, +24dBu
Voutput, Rload variant, Gain variant as noted below)
Non-Inverting Condition
Rload = 75 Ω, Gain= 40dB
Rload = 75 Ω, Gain= 20dB
Rload = 600 Ω, Gain= 40dB
THD+N Characteristics (Ta=25°C, Vs=±24V, 1.0Vrms input, Rs=600
unless otherwise noted)
Total Harmonic Distortion+Noise Inverting Unity Gain vs Frequency
Blue Trace: measured 990Enh THD+N
Brown Trace: analyser noise floor limit
Total Harmonic Distortion+Noise, Non-Inverting, Rload=75 Ω, +24dBu
Audio Precision
THD+N RL=75 40dB 24dBu
08/18/15 09:50:11
output, 40dB gain verses Frequency
THD+N Ratio vs FREQUENCY
0.1
0.0011%
0.0006%
0.00085%
0.01
0.005
0.05
0.02
0.002
0.01
0.005
%
0.001
%
0.002
0.0005
0.001
0.0005
0.0002
0.0002
0.0001
20
0.0001
20
50
100
200
500
1k
2k
5k
10k
50
100
200
500
1k
20k
Hz
Total Harmonic Distortion+Noise Inverting 20db Gain vs Frequency
Blue Trace: measured 990Enh THD+N
Brown Trace: analyser noise floor limit
THD+N Ratio vs FREQUENCY
2k
5k
10k
20k
50k
100k
Hz
Total Harmonic Distortion+Noise, Non-Inverting, Rload=75 Ω, +24dBu
Audio Precision
THD+N RL=75ohm 20dB NonInverting 24dBu 08/18/15 09:50:11
output, 20dB
gain verses Frequency
0.01
0.1
0.005
0.05
0.02
0.002
0.01
0.005
%
%
0.002
0.001
0.0005
0.001
0.0005
0.0002
0.0002
0.0001
20
50
100
200
500
1k
2k
5k
10k
0.0001
20
20k
Total Harmonic Distortion+Noise Non-Inverting 20db Gain vs Frequency
Blue Trace: measured 990Enh THD+N
Brown Trace: analyser noise floor limit
THD+N Ratio vs FREQUENCY
50
100
200
500
1k
2k
5k
10k
20k
50k
100k
Hz
Total Harmonic Distortion+Noise, Non-Inverting, Rload=600 Ω, +24dBu
output, 40dB
gain verses Frequency
Audio Precision
THD+N RL=600ohm 40dB NonInverting 24dBu 08/18/15 09:50:11
0.1
0.01
0.05
0.005
0.02
0.01
0.002
0.005
%
%
0.002
0.001
0.001
0.0005
0.0005
0.0002
0.0002
0.0001
20
50
100
200
500
1k
2k
5k
10k
0.0001
20
20k
Hz
50
100
200
500
1k
2k
5k
10k
20k
50k
100k
Hz
©1998-2015 Sonic Imagery Labs
Specifications subject to change without notice
REV D, 8.20.2015
Page Sonic Imagery Labs
P.O. Box 20494
Castro Valley, California 94546
P:(510)728-1146 F:(510)727-1492
www.sonicimagerylabs.com
Model 990Enh-Ticha Discrete Operational Amplifier
Professional Audio Products Datasheet
Model 990Enh-Ticha
Discrete Operational Amplifier
THD+N Large Signal Performance (20kHz, Vs=±24V,
+24dBu Voutput, Rload variant, Gain variant as noted below)
Inverting Condition
Rload = 75 Ω, Gain= 40dB
Rload = 75 Ω, Gain= 20dB
Rload = 600 Ω, Gain= 40dB
0.00095%
0.00071%
0.00075%
Gain Accuracy vs Frequency (Ta=25°C, Vs=±24V unless otherwise noted)
Total Harmonic Distortion+Noise, Inverting, Rload=75 Ω, +24dBu output,
Audio Precision
THD+N RL=75 24dBu 40dB Gain
08/18/15 09:53:04
40dB gain
verses Frequency
20dB (Av=10) Non inverting gain vs Frequency
+3
+2.25
0.01
+1.5
0.005
d
B
r
0.002
+0.75
-0
-0.75
-1.5
%
0.001
-2.25
-3
20
0.0005
50
100
200
500
1k
2k
5k
10k
20k
50k
100k
10k
20k
50k
100k
Hz
40dB (Av=100) Non inverting gain vs Frequency
0.0002
0.0001
20
+3
+2.25
50
100
200
500
1k
2k
5k
10k
20k
50k
100k
+1.5
Hz
Total Harmonic Distortion+Noise, Inverting, Rload=75 Ω, +24dBu output,
Audio Precision
THD+N RL=75 24dBu 40dB Gain
08/18/15 09:53:04
20dB gain verses Frequency
+0.75
d
B
r
-0
-0.75
0.01
-1.5
0.005
-2.25
-3
20
0.002
%
50
100
200
500
1k
2k
5k
Hz
Linearity vs Amplitude (Ta=25°C, Vs=±24V unless otherwise noted)
0.001
+3
+2.5
0.0005
+2
+1.5
+1
0.0002
0.0001
20
50
100
200
500
1k
2k
5k
10k
20k
50k
100k
d
B
g
Hz
+0.5
+0
-0.5
-1
Total Harmonic Distortion+Noise, Inverting, Rload=600 Ω, +24dBu output,
Audio Precision
THD+N RL=600 24dBu 40dB Gain
08/18/15 09:53:04
40dB gain verses Frequency
-1.5
-2
-2.5
0.01
-100
-80
-60
0.005
-40
-20
+0
+20
dBV
THD+N vs Amplitude (Ta=25°C, Vs=±24V unless otherwise noted)
0.002
%
+0
-20
0.001
-40
d
B
u
0.0005
-60
-80
0.0002
-100
0.0001
20
50
100
200
500
1k
2k
5k
10k
20k
50k
100k
-60
Hz
-50
-40
-30
-20
-10
+0
+10
+20
dBV
©1998-2015 Sonic Imagery Labs
Specifications subject to change without notice
REV D, 8.20.2015
Page Sonic Imagery Labs
P.O. Box 20494
Castro Valley, California 94546
P:(510)728-1146 F:(510)727-1492
www.sonicimagerylabs.com
Model 990Enh-Ticha Discrete Operational Amplifier
Professional Audio Products Datasheet
Model 990Enh-Ticha
Discrete Operational Amplifier
THD Residual+N Characteristics (Ta=25°C, Vs=±24V, 0dBV input,
Input-Output Phase Characteristics (Ta=25°C, Vs=±24V, 0dBV input,
Rs=600 Ω Rload=10K Ω unless otherwise noted)
Rs=600 Ω Rload=10K Ω unless otherwise noted)
1kHz Fundamental @ 0dBV, 6dB gain (Av=2) Non inverting vs Frequency
Non inverting input 6dB gain (Av=2) vs Frequency
+10
+0
+8
-20
+6
+4
-40
d
e
g
-60
d
-80
B
+2
+0
-2
-4
-100
-6
-120
-8
-140
-10
10
20
50
100
200
500
1k
2k
5k
10k
20k
50k
200k
Hz
-160
1
2
5
10
20
50
100
200
Hz
500
1k
2k
5k
10k 20k
+
IN
NON-INVERTING
OUT
-
Broadband Noise Characteristics (Ta=25°C, Vs=±24V, Rs=0 Ω to
gnd, Rload=10K Ω unless otherwise noted)
Rf
10.0K
Rg
10K
Cc
15pF
Non inverting, 6dB gain (Av=2) 22Hz to 22kHz NBW vs Time
Inverting input 0dB gain (Av=0) vs Frequency
-170
-172
-174
-176
d
e
g
-178
-180
-182
-184
-186
-188
-190
10
20
50
100
200
500
1k
2k
5k
10k
20k
50k
200k
Hz
Cc
15pF
NON-INVERTING
IN
+
Rg
10K
Rf
10.0K
20Hz to 22Khz
BANDPASS
(see Jung)
x1000
IN
OUT
Rg
10.0K
+
Rf
10.0K
OUT
INVERTING
Rg
4.99K
Cc
15pF
©1998-2015 Sonic Imagery Labs
Specifications subject to change without notice
REV D, 8.20.2015
Page Sonic Imagery Labs
P.O. Box 20494
Castro Valley, California 94546
P:(510)728-1146 F:(510)727-1492
www.sonicimagerylabs.com
Model 990Enh-Ticha Discrete Operational Amplifier
Professional Audio Products Datasheet
Model 990Enh-Ticha
Discrete Operational Amplifier
Power Supply Rejection Ratio Characteristics (Ta=25°C,
Vs=±24V, Rs=0 Ω to Gnd Rload=10K Ω unless otherwise noted)
Open Loop Frequency Response (Ta=25°C, Vs=±24V, Rload=100K Ω
unless otherwise noted)
Non inverting, Unity gain (Av=1) vs Frequency, Positive Supply
+130
+10
+120
+0
+110
-10
+100
-20
+90
-30
+80
GAIN (dB)
-40
-50
d
B -60
+70
+60
-70
+50
-80
+40
-90
+30
-100
+20
-110
+10
-120
-130
20
50
100
200
500
1k
2k
5k
10k
20k
50k
+0
1
100k 200k
2
5
10 20
50 100 200
500 1k 2k
5k 10k 20k
Non inverting, Unity gain (Av=1) vs Frequency, Negative Supply
+10
500k 1M 2M
5M 10M 20M50M
Full Power Frequency Response (Ta=25°C, Vs=±24V, Rload=600 Ω
unless otherwise noted)
+0
-10
+25
-20
+24.5
-30
+24
-40
+23.5
-50
d
B -60
+23
+22.5
-70
d
B
V
-80
-90
+22
+21.5
+21
-100
+20.5
-110
+20
-120
-130
20
50k 100k
Hz
Hz
50
100
200
500
1k
2k
5k
10k
20k
50k
+19.5
100k 200k
Hz
+19
20
50
100
200
500
1k
2k
5k
10k
20k
50k
100k
200k
500k
Hz
©1998-2015 Sonic Imagery Labs
Specifications subject to change without notice
REV D, 8.20.2015
Page Sonic Imagery Labs
P.O. Box 20494
Castro Valley, California 94546
P:(510)728-1146 F:(510)727-1492
www.sonicimagerylabs.com
Model 990Enh-Ticha Discrete Operational Amplifier
Professional Audio Products Datasheet
Model 990Enh-Ticha
Discrete Operational Amplifier
Pulse Response Ta=25°C, Vs=±24V RL=600Ω Cc=30pF
Small Signal Inverting Av=-1
Small Signal Inverting Av=-1
Small Signal Non-Inverting Av=2
Small Signal Non-Inverting Av=2
Large Signal Inverting Av=-1
Large Signal Inverting Av=-1
Large Signal Non-Inverting Av=2
Large Signal Non-Inverting Av=2
Table 1. Compatible Upgrade Table
Pulse Response Test Setup
Cc
IN
10.0K
Rf
10.0K
-
Rg
OUT
+
IN
+
Rg
INVERTING
NON-INVERTING
OUT
Rf
Cc
0pF
©1998-2015 Sonic Imagery Labs
Specifications subject to change without notice
REV D, 8.20.2015
The Model 990Enh-Ticha can be used to upgrade and/or replace
these obsolete or end of life discrete operational amplifiers. This
list is by no means comprehensive. Contact Sonic Imagery Labs for
additional information.
Jensen JE990 Series
Automated Processes Inc. API-2520, 2520H, 2525
John Hardy Co. 990A-990C
FiveFish Studios DOA series
Avedis Audio 1122
Seventh Circle Audio SC10, SC25, SC99
Sound Skulptor SK25, SK99, SK47
Yamaha NE80100, NE80200
TOA PC2011
ProTech Audio Model 1000
Purple Audio KDJ3, KDJ4
Modular Devices 1731, 1757
Modular Audio Products (MAP) 5000 Series, 1731 1731A
Melcor 1731
JLM Audio 99V
Inward Connections SPA690
BTI OA400
FAX Audio FA-100
Analog Devices 111
Page Sonic Imagery Labs
P.O. Box 20494
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Model 990Enh-Ticha Discrete Operational Amplifier
Professional Audio Products Datasheet
Model 990Enh-Ticha
Discrete Operational Amplifier
Application Notes
Low leakage film capacitors with high-quality dielectric
(polypropylene or COG-NPO ceramic) should be used. Low-ESR
power supply bypass capacitors with a small resistance in series
with the power supply rails are essential for low noise operation.
Precision low noise 1% metal film resistors should always be used.
Since these components can represent high impedance, lead
length and trace lengths should be minimized. Assembled circuits
and PCB’s should be carefully cleaned of flux residue to prevent
leakage paths or other spurious behavior.
Figure 2. Transformer input mic preamp
R1
36-43Ω
T1
JT-16-B
OUT
+IN
L1
3.6-4.3uH
-IN
Figure 1. Isolating capacitive loads with an inductor. The
non-inductive resistor avoids resonance problems with load
capacitance by reducing Q.
red
ylw
brn
orn
wht
blk
R2
3.57K
-
Figure 2 shows a simple traditional transformer input mic preamp,
with a fixed gain of 26.5dB (Av=21.2). The Jensen JT-16-B mic input
transformer is perfectly suited for this application.
C1
610pF
+
Typical Applications
R1
6.19K
IN
The resistor kills the Q of series resonant circuits formed by
capacitive loads. A low inductance resistor is recommended.
Optimum values of L and R depend upon the feedback gain and
expected nature of the load, but are not critical.
+
R4
100Ω
U1
990Enh
R3
1.00KΩ
R5
36-43Ω
L1
3.6-4.3uH
C4
470uF
OUT
R6
10K
C2
510pF
C3
1000uF
The 990Enh is normally stable with resistive, inductive or smaller
capacitive loads. Larger capacitive loads interact with the openloop output resistance to reduce the phase margin of the feedback
loop, ultimately causing oscillation.
With loop gains greater than unity, a speedup capacitor across
the feedback resistor will aid stability. In all cases, the op amp
will behave predictably only if the supplies are properly bypassed,
ground loops are controlled and high-frequency feedback is derived
directly from the output terminal.
So-called capacitive loads are not always capacitive. A high-Q
capacitor in combination with long leads or PCB traces can present
a series-resonant load to the op amp. In practice, this is not usually
a problem; but the situation should be kept in mind.
Large capacitive loads (including series-resonant) can be
accommodated by isolating the feedback amplifier from the load
as shown in Figure 1. The inductor gives low output impedance at
lower frequencies while providing an isolating impedance at high
frequencies.
R1, R2 and C3 provide match and termination for the JT-16-B input
transformer. The step up nature of the transformer provides 5.6dB
of voltage gain. R3 and R4 set ac voltage gain of the 990Enh opamp. Whereas, R3/R4+1=Av, 20logAv=Gain_dB. Other values can
be chosen depending on gain desired. C2 provides phase-lead
compensation and sets the upper frequency BW cutoff point.
270pf= 410kHz, 510pF=260kHz, 750pF=180kHz and 1000p= 150kHz. C3
keeps the DC gain of the 990Enh at unity so that a small difference
between the DC volatges at the inputs will not produce large offset
voltages at the output.
With multiple stages of gain, the accumulation of DC offsets of
various amplifiers can lead to problems. The classical solution to
decoupling the offset has been to employ capacitors C3 and C4. A
superior method which eliminates the need for C3 and C4, which
has come into vogue over the last couple of decades, is the use of
a servo amplifier stage, for output DC-offset elimination. The circuit
shown in Figure 3. is the basic noninverting audio preamp (U1)
from Figure 2. with a noninverting integrator feedback stage (U2)
connected around it. For normal audio range input signals, the gain
of this stage is defined conventionally.
©1998-2015 Sonic Imagery Labs
Specifications subject to change without notice
REV D, 8.20.2015
Page Sonic Imagery Labs
P.O. Box 20494
Castro Valley, California 94546
P:(510)728-1146 F:(510)727-1492
www.sonicimagerylabs.com
Model 990Enh-Ticha Discrete Operational Amplifier
Professional Audio Products Datasheet
Model 990Enh-Ticha
Discrete Operational Amplifier
Typical Applications (continued)
In this instance, the resistance to ground is made up of the parallel
equivalent resistances of R4 and R5; basically Av=1+R3/(R4//R5).
C3-R7 and C4-R6 form the integration time constants, which are set
equal in this form of integrator. The DC feedback from the U2 stage
is applied to the inverting input of U1, via R4.
The power supply voltages should be sufficient enough to
accommodate the worst DC offset of U1 that can be expected from
inputs.
Note that, in principal, a noninverting integrator could also be used,
with DC correction applied to the inverting input junction of U1. The
inverting integrator is simpler overall, however, and it eliminates
one RC network.
Figure 4. Summing Amplifier with servo.
Figure 3. Transformer input mic preamp with servo.
R5
100Ω
-
OUT
L1
3.6-4.3uH
R3
1.00KΩ
+
U2
-
C3
0.1uF
Vin1
Vin2
R6
1MΩ
C2
510pF
R4
10KΩ
Cx
91 pF
Riso
36-43Ω
Vin3
C4
0.1uF
Vin4
Vinx
R7
1MΩ
Viny
By virtue of the integrator stages’ infinite gain at DC, the overall loop
will force the output of U1 to an extremely low DC level. In practice,
the residual DC output offset of U1 becomes essentially the offset
voltage of U2.
The DC feedback resistor, R4 is chosen to be 10X higher than R3,
while the integrator time constant sets the basic low frequency
rolloff point. In this example, the rolloff is set at about 0.165Hz.
Low leakage clamping diodes can be added across C4 to prevent
latchup. U2 should be a precision low offset voltage, low input bias
current, FET input type device similar to an AD711.
An inverting summing amplifier with servo correction is shown in
Figure 4; it uses the more familiar form of inverting integrator for DC
offset correction. In this circuit U1 is a basic inverting gain stage,
with a voltage gain of RFB/Rsumn. The DC feedback from from the
U2 integrator stage is applied to U1 through the divider R4-R5. The
time constant and scaling of resistor values are the same as the
circuit in Figure 3.
Vinz
Rsum1
Rsum2
Liso
3.6-4.3uH
JP1
Rsum3
STRAY
CAPACITANCE
wht
blk
+
R5
36-43Ω
Rsum4
Rsumy
Rsumz
RFB
10KΩ
Riso
36-43Ω
-
+
OUT
U1
990Enh
Liso
3.6-4.3uH
R6
1MΩ
C4
0.1uF
R4
100KΩ
Rsumx
JP2
orn
R2
3.57K
brn
U1
990Enh
Ccomp
-IN
red
R1
6.19K
+IN
ylw
C1
610pF
T1
JT-16-B
R5
1KΩ
U2
+
Ac Voltage Gain, Each Channel= RFB/Rsum
Ac Voltage Gain Overall= RFB/Rsum1//Rsum2//Rsum3...etc
With many inputs being summed, the output of the summing amplifier
could become excessive. The final value for Rsum is chosen based
on the number of channels, input signal levels, maximum peak
voltages, etc.
If the servo (U2 R4 C4 R6) circuit is not used, the non-inverting input
may be tied to ground directly, or through resistor R5. The value of
this resistor should be adjusted to equal the DC source resistance
of all the input resistors (Rsum) seen by the inverting input, which
is the parallel resistance of all input resistors (assuming they are
not AC coupled) and the feedback resistor (Rsum//RFB) When both
inputs of the 990Enh see identical source resistances, the output
offset voltage will be at its lowest value. This resistor can result in
increased noise when compared to a grounded input. This problem
can be overcome by a parallel capacitor (Ccomp). The capacitor
value is not critical, with 0.1uF being a good starting point.
©1998-2015 Sonic Imagery Labs
Specifications subject to change without notice
REV D, 8.20.2015
Page 10
Sonic Imagery Labs
P.O. Box 20494
Castro Valley, California 94546
P:(510)728-1146 F:(510)727-1492
www.sonicimagerylabs.com
Model 990Enh-Ticha Discrete Operational Amplifier
Professional Audio Products Datasheet
Model 990Enh-Ticha
Discrete Operational Amplifier
PCB Sockets for 990Enh-Ticha
Typical Applications (continued)
The physical terminating point or summing junction for the noninverting input is critical. In applications where many inputs are
to be summed together, it is important to remember that although
each input may be at unity gain, the overall gain of the summing
amplifier is higher. If the non-inverting inputs are terminated far
from the signal sources being summed and noise is coupled into this
junction, the noise is amplified by the overall gain of the summing
amp. The 990Enh is the lowest noise discrete operational amplifier
available, but poor layout, grounding or system architecture can
defeat this advantage.
Long summing busses create stray capacitance at the inverting
input, resulting in phase-shift of the feedback signal. When the
capacitance becomes excessive, this will cause the summing
amplifier to oscillate at ultra-high frequencies. Capacitance can
be added across RFB (Cx) to limit the high frequency response.
Additionally Riso-Liso can be inserted between the summing buss
and the inverting input. It maintains normal audio performance by
providing a low impedance throughout the audio bandwidth, while
isolating stray capacitance by providing high impedance at ultrahigh frequencies.
It is highly recommended that the user not solder the pins directly
to the mating printed circuit board. Overheating the pin creates a
cold solder joint at the other end. Permanant soldering of the pin
prevents easy removal of the module. Lastly, soldering prevents one
from servicing components which may lie underneath the module.
Many types of sockets for 0.040” diameter pins are available from
several manufacturers. Sonic Imagery Labs uses and stocks the
sockets from all three listed manufacturers below. These sockets
can be soldered or swaged in your printed circuit board. Additionally,
users can purchase a set of six from Sonic Imagery Labs online.
Mill-Max
190 Pine Hollow Road,
PO Box 300
Oyster Bay NY 11771
Part Number 0344-2-19-15-34-27-10-0
Wearnes Cambion Ltd
Peverial House
Mill Bridge, Castleton
Hope Valley S33 8WR
United Kingdom
Part Number 450-3756-02-03
Concord Electronics Corp Part Number 09-9035-2-03
33-00 47th Ave, Level 1A
Long Island City, NY 11101
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Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and whose failure to perform when properly used in accordance with
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©1998-2015 Sonic Imagery Labs
Specifications subject to change without notice
REV D, 8.20.2015
Page 11
Sonic Imagery Labs
P.O. Box 20494
Castro Valley, California 94546
P:(510)728-1146 F:(510)727-1492
www.sonicimagerylabs.com